Another study revealed that adults with a genetic vulnerability to the psychosis-inducing properties of cannabis (Val/Val carriers on the catechol-O-methyltransferase (COMT) gene) were significantly more impaired on verbal and visual memory (not learning) following Δ9-THC exposure, relative to those with a low genetic vulnerability (Met/Met and Val/Met carriers) (59). Here, COMT is linked to psychotic disorder.